1. Field of the Invention
The present invention relates to a liquid crystal display (LCD) device, and more particularly, to a backlight assembly for an LCD device.
2. Discussion of the Related Art
In recent years, various flat panel display devices, such as a liquid crystal display (LCD), a plasma display panel (PDP), an electroluminescent display (ELD), and a vacuum fluorescent display (VFD), have been developed. Among the various flat panel display devices, liquid crystal display (LCD) devices have been most widely used instead of cathode ray tube (CRT) devices because they are thin, light, and consumes less power. LCD devices have been used for desktop and mobile computer monitors, and televisions display.
Advances in picture quality enhancement for LCD devices have been lagging, in some respects, other features and advantages of the LCD devices. Picture quality improvement is needed for using LCD devices as general purpose displays in various applications. For example, in addition to being light, thin and low-powered, LCD devices need provide high resolution and high luminance on a large-sized screen.
In general, an LCD device includes an LCD panel for displaying a picture image, and a driving part for applying a driving signal to the LCD panel. The LCD panel includes first and second glass substrates being bonded to each other at a predetermined interval therebetween, and a liquid crystal material injected between the first and second glass substrates.
The first glass substrate includes a plurality of gate and data lines, a plurality of pixel electrodes, and a plurality of thin film (TFT) transistors. The first glass substrate is also called a TFT array substrate. The gate lines are formed on the first glass substrate at fixed intervals. The data lines are formed perpendicular to the plurality of gate lines at fixed intervals. Crossings of the gate lines and the data lines define pixel regions. The plurality of pixel electrodes, arranged in a matrix-type configuration, are respectively formed in the pixel regions. The thin film transistors are switched in response to signals from the gate lines and transmit signals from the data lines to the respective pixel electrodes.
The second glass substrate (color filter substrate) includes a black matrix layer, an RGB color filter, and a common electrode. The black matrix layer blocks light transmission except within the pixel regions of the first substrate. The RGB color filter layer provides color display capability. The common electrode, together with the pixel electrodes, controls light transmission for displaying a desired image. A predetermined distance is maintained between the first and second glass substrates by spacers. The first and second substrates are bonded to each other by a sealant.
In general, an LCD device requires an external light source for proper operation. For example, in a transmitting type LCD device, a backlight is required for emiting and guiding light to a rear surface of the LCD panel. The backlight may a direct type or an edge type.
In the direct type backlight, a silhouette of a fluorescent lamp may be reflected on the LCD panel. Thus, a predetermined interval should be maintained between the fluorescent lamp and the LCD panel. The direct type backlight requires a light-scattering device to provide a light source of uniform luminance. Further, the size of the light-emitting surface in the backlight increases in accordance with the size of the panel. The size of the direct type backlight has an impact on the thickness of the light-scattering device. If the thickness of the light-scattering device is not appropriate, the light-emitting surface is not flat.
In the edge type backlight, a cylindrical fluorescent lamp is placed at one side of the LCD panel. A light-guiding plate is installed to transmit the light emitted from the fluorescent lamp to the entire surface of the LCD panel. The edge type backlight has low luminance. Also, appropriate optical design and processing technology of the light-guiding plate rare required to obtain uniform luminance. Recently, two bending-type light sources have been used in the edge type backlight to achieve uniform luminance.
FIG. 1 is a schematic view illustrating a backlight assembly using a bending-type light source according to a related art arrangement. FIG. 2 is a schematic view illustrating a printed circuit board (PCB) provided on a rear surface of the related art light-guiding plate depicted in FIG. 1. Referring to FIG. 1 and FIG. 2, the related art backlight assembly is provided with a first light source 11a, a second light source 11b, a first inverter 21a, and a second inverter 21b. The first light source 11a emits light toward a light-guiding plate 12. The first light source 11a is bent in an L-shape along one long side and one short side of the light-guiding plate 12. The second light source 11b, which emits toward the light-guiding plate 12, in bent in an L-shape along the other long side and the other short side of the light-guiding plate 12. The first inverter 21a provides a high voltage H and a low voltage L to the first light source 11a. The second inverter 21b provides a high voltage H and a low voltage L to the second light source 11b. 
A wire 10a for the high voltage H and a wire 10b for the low voltage L are provided at both ends of the first light source 11a. The wire 10a for the high voltage H and the wire 10b for the low voltage L are also provided at both ends of the second light source 11b. Furthermore, a first connector 13a and a second connector 13b are provided to the backlight assembly. The first connector 13a is connected to the wire 10a for the high voltage H and the wire 10b for the low voltage L of the first light source 11a. The second connector 13b is connected to the wire 10a for the high voltage H and the wire 10b for the low voltage L of the second light source 11b. The first connector 13a is connected to the first inverter 21a, and the second connector 13b is connected to the second inverter 21b. 
A plurality of light-diffusion members (not shown) and an LCD panel (not shown) are provided on the light-guiding plate 12. The light-diffusion members are provided with a light-diffusion sheet and a polarizing film. The light-diffusion sheet scatters and diffuses light emitted from the first and second light sources 11a and 11b through the light-guiding plate 12. Also, the polarizing film is provided on the light-diffusion sheet to receive the diffused light from the light-diffusion sheet and to transmit light with improved luminance toward a display area of the LCD panel.
In addition, a U-shaped lamp housing (not shown) having an open side toward the light-guiding plate 12 may be provided in the circumference of the light sources 11a and 11b to obtain a smooth transmission of the light emitted from the light sources 11a and 11b to the light-guiding plate 12. A reflective sheet (not shown) may be provided below the light-guiding plate 12 to reflect light leaking through the lower side of the light-guiding plate 12 tooward the display part of the LCD panel, thereby reducing light loss.
Referring to FIG. 2, a printed circuit board (PCB) 20 is provided on a rear surface of the light-guiding plate 12. The first and second inverters 21a and 21b are mounted on the PCB 20 to provide a driving voltage to the first and second light sources 11a and 11b. A first and a second transformers (not shown) are provided to each of the first and second inverters 21a and 21b to supply the high voltage H and the low voltage L to both sides of each of light sources 11a and 11b. The first transformer for the first inverter 21a outputs the high voltage H. Then, the high voltage H is transmitted to the first connector 13a along a first metal pattern 15a of the PCB 20. The high voltage H inputted to the first connector 13a is applied to one side of the first light source 11a through the wire 10a. The second transformer for the first inverter 21a outputs the low voltage L. Then, the low voltage L is transmitted to the first connector 13a along another first metal pattern 15a of the PCB 20. The low voltage L inputted to the first connector 13a is applied to the other side of the first light source 11a through the wire 10b. 
Similarly for the second inverter 21b, the high voltage H and the low voltage L of the first and second transformers are respectively applied to one side and the other side of the second light source 11b through the wire 10a and the wire 10b, both of which are connected to the second connector 13b. The second connector 13b and the output terminals for the high voltage H and the low voltage L in the respective transformers of the second inverter 21b are connected with a second metal pattern 15b. 
Meanwhile, the first inverter 21a applies the high voltage H and the low voltage L to the both sides of the first light source 11a. One of the wire 10a and the wire 10b, which are connected to both sides of the first light source 11a, becomes longer than the other. Similarly, the second inverter 21b applies the high voltage H and the low voltage L to the both sides of the second light source 11b. One of the wire 10a and the wire 10b, which are connected to both sides of the second light source 11b, becomes longer than the other.
As shown in FIGS. 1 and 2, the wire 10b is longer than the wire 10a. However, the wire 10a can be made longer than the wire 10b. In the case of small-sized LCD devices having mechanical restrictions, especially, LCD devices for vehicles, the difference in length in the wires makes it difficult to obtain a thin LCD device.